I decided to dig out both.
Car Park:
e-Document - 102834-dpp-0001.pdf
A6MARR:
http://www.semmms.info/140683/435117/fullschemedrawing
So the car park will come in via Shadowmoss from Ringway Rd at a T-Junction (and also from Styal Rd). When the A6MARR is built, the T-junction of Ringway Road and Shadowmoss Road will be smoothed out to become a curve on one continuous road as mentioned by Shed-on-a-Pole.
The A6MARR drawing is not at a great scale but suggests to me that cycle and pedestrian access only will be provided between the two although this could change. It is my understanding that when the A6MARR was in its early stages of design the 9,000 car park wasn't there although it's worth thinking about the number of trips it might generate in the context of long stay car parking.